BMW B48 / B38 engine: faults and reliability

• B38 1.5 136 hp (MINI Cooper, 118i)

  since 2014 · 136 hp · B38A15, B38B15

  Buy

  We have found no serious, widespread fault documented specifically for the B38; it shares with the rest of the family the same watch points around the cooling circuit and the oil seals.^[2]

• B48 2.0 178-197 hp (120i, 220i, 320i, 520i, X1/X2/X3 20i, MINI Cooper S)

  since 2014 · 178–197 hp · B48A20, B48B20

  Buy

  It is the most widely fitted B48 version and has no serious, widespread fault on record; it is worth checking the cooling circuit and any oil leaks next to the turbo and the VANOS.^[2]

• B48 2.0 252-258 hp (330i, 530i, X3/X4 xDrive30i)

  since 2015 · 252–258 hp · B48A20, B48B20

  Buy

  It shares its block and architecture with the rest of the B48; we have found no serious, widespread fault on record that is specific to this more powerful version.^[2][6]

• B48 2.0 up to 302-312 hp, high performance (MINI John Cooper Works, BMW X1 M35i)

  since 2015 · 302–312 hp · B48A20, B48C20

  Buy

  We have found no serious, widespread fault on record that is specific to the higher-output versions of the B48, beyond the watch points common to the whole family (cooling, oil seals).^[2]

Buy: No known serious faults, or they have already been corrected, in this version. With caution: Worth buying if something specific is verified: history, a replaced part or a completed campaign. Avoid: High risk of a serious fault that is hard to check for or prevent.

1. 1Medium severityFrequency: OccasionalCoolingDeterioration of hoses and seals in the cooling circuit, with coolant lossYes: over the years and many heat cycles, the hoses, the expansion tank and some of the plastic seals in the B48/B38 cooling circuit can deteriorate and lose coolant, sometimes without any visible puddle under the car.
2. 2Medium severityFrequency: OccasionalLubricationOil leaks or seepage from seals and covers, near the turbo and the VANOSYes: over time, oil seepage or leaks can appear at seals, covers and crankcase ventilation connections, in an area of the engine close to the turbo and the VANOS system.
3. 3High severityFrequency: RareTimingTiming chain on the early units (2014-2018), redesigned in the B48TUWe have found no documented cases of timing chain breakage on the B48. The one concrete fact that does exist is that BMW redesigned the chain as a single piece in the 2018 B48TU update, which points to an area for improvement in engines built before that date.
4. 4Low severityFrequency: CommonIntakeCarbon build-up on the intake valves (direct injection)Yes, as on most direct-injection engines: because they are not washed by fuel, the intake valves on the B48/B38 build up carbon over the years, especially in urban use, with a loss of smoothness and a less stable idle.

Severity colours: low, medium, high, critical. How we rate them

Manufacturer

BMW

Family

Familia modular B (motores de tres y cuatro cilindros turbo de BMW)

Fuel

Petrol

Displacement

1,998 cm³

Cylinders

4

Fuel system

Turbo

Injection

Direct injection

Timing

Chain

Power

136–312 hp

Peak torque

450 Nm

Production

since 2014

Makes

BMW and MINI

Technical data^[1][4][5]

1. since 2014

   B38 1.5 136 hp (MINI Cooper, 118i)

   The entry-level version of the family, with three cylinders, 1.5 litres and a turbo; it powers the MINI Cooper (F55/F56/F60) with 136 hp (100 kW) and, at BMW, the 118i.^[4][7][8]

2. since 2014

   B48 2.0 178-197 hp (120i, 220i, 320i, 520i, X1/X2/X3 20i, MINI Cooper S)

   The middle power step of the B48 and the most widespread: it powers the 120i, 220i, 320i (in its entry-level version), 520i, the sDrive20i/xDrive20i variants of the X1, X2 and X3, and the MINI Cooper S, with published factory outputs of between 178 and 197 hp (131-145 kW) depending on the model and year.^[1][8]

3. since 2015

   B48 2.0 252-258 hp (330i, 530i, X3/X4 xDrive30i)

   The higher-output step of the standard B48 (short of the John Cooper Works versions), with a higher-flow turbine; it powers the 330i and 530i, with published figures of around 255 hp, and the xDrive30i variant of the X3 and X4.^[6]

4. since 2015

   B48 2.0 up to 302-312 hp, high performance (MINI John Cooper Works, BMW X1 M35i)

   A more aggressive tune of the B48 for the sporty variants: the MINI John Cooper Works "GP" (limited edition, from 2020) reaches 302 hp (225 kW) and the BMW X1 M35i 312 hp. The regular (non-GP) John Cooper Works uses an equally strengthened version of the B48, though we have not found a verified official power figure for all its generations.^[6][8]